Friend just bought a house. Saw it yesterday for first time. Have never seen floors like this. LR is maybe 20 x 14. In the middle is a hump maybe 2″ above the far sides. It’s stiff. But walk towards the walls on either side of that centerline, and you start bouncing like those guys in the WWF ring. Without trying, I could make cabinet doors unlatch. Her ex said he thinks there’s a steel beam down the middle in the short direction, which would be the hump. Same situation and measurements in kitchen.
I went to the crawlspace. 5′ at the front edge and 0 at the back. Framed with 2 x 8 16oc spanning the 14′. Plus they cantilever at least 5′ out to create a porch, which seems excessive. Didn’t have enough time to check the foundation supporting all of this and was too dark to catch other details.
Any suggestions for what to look for the next time DW and I visit? Or what measurements to take so I can eventually ask the question here: what’s the easiest way to stiffen the floor (i.e., biggest bang for the buck)? My first thought is to take a few concrete blocks and boards over. Split the distance from the beam to the wall. Give a few blocks a good flat base. Build up boards to the joists, get a wedge in there and tighten it all up. Might have to add some blocking be/t joists (couldn’t see any) to avoid racking them. This sound good or bad? (I wouldn’t do anything w/o more info regardless.)
Thanks. Jim
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It sounds like you have the problem pretty well figured out and you are right about the solution. A girder down the center will cut the span in half and at a reasonable cost with having to move wiring or pipes. I have seen this solution in dozens of houses. I have also seen it poorly done in most of those houses. The usual problem is that there are no legitamate footers under the columns that support the girder. The blocks that usually are used settle into the dirt and the post is left dangling and the floor is as springy as before. You need to dig down to undisturbed earth and pour a lightly reinforced footing 8"x24"x24". I would put the girder in before the posts and jack it up til you are satisfied with the plane of the floor and then put in your posts. It will be a lot of fun crawling around on your belly.
Fourteen feet is way, way too long for a 2X8 floor. Adding a beam or sistering deeper joists sounds like the only way to go to me.
The 2" hump doesn't do much for me - I'd try to figure out the source of that problem while I was at it.
I see that "whale back" hump in a lot of older buildings here. What they did is they put the same size and spacing of piers and posts under the internal bearing walls and under the floors. The far greater weight of the bearing walls causes them to settle farther than the middles of the floors. Step one is to get in there with a laser level, carefully measure and draw a plan of the pier and post foundation with the distance from your level line to the sub floor noted for each post. Then figure out how much to trim the posts to straighten out the floor. If the joists have some residual crown from being bent all those years, buy a grand piano. ;-)
-- J.S.
Have a look in the Gallery. I posted some pictures of crawl space work under "New Footing in the Middle of the House"
-- J.S.
Thanks John, I'll head there next.